The present disclosure relates to an integrator circuit, and more particularly, to a noise-robust integrator circuit.
Display devices such as a liquid crystal display and organic light emitting display, portable communication devices, and information processing devices, and etc. perform their functions using various input devices. As a type of such input devices, touch screen devices are being widely used in portable phones, smart phones, palm-size PCs, and automated teller machines (ATM).
Touch screens perform desired commands, by contacting a finger, touch pen, or stylus on their screens to write text or draw and execute program codes by selecting icons. Touch screen devices can sense whether a finger or touch pen has been contacted on the surface of themselves and determine the contact position.
Touch screens may be sorted into resistive type and capacitive type touch screens according to their touch sensing method.
A resistive type touch screen has a configuration where resistive material is coated on a glass or transparent plastic plate and then polyester film is covered thereon. The resistive type touch screen detects resistance variation to sense a touch point when its screen is touched. The resistive type touch screen has a limitation of being incapable of sensing a touch input when touch pressure is weak.
A capacitive type touch screen may be supplied by forming electrodes at both or one side of a glass or transparent plastic plate. The capacitive type touch screen can detects a touch point by applying a voltage between two electrodes and then analyzing a variation of capacitance between the two electrodes when an object, such as a finger, touches its screen.
A capacitive type touch screen requires a circuit for measuring capacitance formed at one electrode or between two electrodes to sense a touch point. Such capacitance measuring circuits have been used mainly for measuring capacitances of various circuits or devices. However, because various portable devices now provide touch input interfaces, the application range of capacitance measuring circuits for sensing a contact or proximity of a user is expanding.
Capacitance measuring circuits used for touch screens of typical portable phones have limitations in that malfunctions arise by various noises caused by changes in the surrounding environments.